Assessment of the Biological Similarity of Three Capsaicin Analogs (Capsinoids) Found in Non-Pungent Chili Pepper (CH-19 Sweet) Fruits

Effects of phenylcapsaicin on aerobic capacity and physiological parameters in active young males: a randomized, triple-blinded, placebo-controlled, crossover trial

Objective: Phenylcapsaicin (PC) is a new capsaicin analog which has exhibited a higher bioavailability. This sudy assessed the effects of a low dose (LD) of 0.625 mg and a high dose (HD) of 2.5 mg of PC on aerobic capacity, substrate oxidation, energy metabolism and exercise physiological variables in young males. Materials and methods: Seventeen active males (age = 24.7 ± 6.0 years) enrolled to this randomized, triple-blinded, placebo-controlled, crossover trial. Participants attended the laboratory on 4 sessions separated by 72-96 h. A submaximal exercise test [to determine maximal fat oxidation (MFO) and the intensity at MFO (FATmax)] followed by a maximal incremental test (to determine VO2_max) were performed in a preliminary session. The subsequent sessions only differed in the supplement ingested [LD, HD or placebo (PLA)] and consisted of a steady-state test (60 min at FATmax) followed by a maximal incremental test. Energy metabolism, substrate oxidation, heart rate, general (gRPE) and quadriceps (RPEquad) rate of perceived exertion, skin temperature and thermal perception were tested. Results: Clavicle thermal perception was lower in HD compared to PLA and LD (p = 0.04) across time. HD reduced maximum heart rate in comparison to PLA and LD (p = 0.03). LD reported higher general RPE (RPEg) values during the steady-state test compared to PLA and HD across time (p = 0.02). HD and LD elicited higher peak of fat oxidation during the steady-state test compared with PLA (p = 0.05). Intra-test analyses revealed significant differences for fat oxidation (FATox) in favor of HD and LD compared to PLA (p = 0.002 and 0.002, respectively), and for carbohydrate oxidation (CHOox) (p = 0.05) and respiratory exchange ratio (RER) (p = 0.03) for PLA. In the incremental test, only general RPE at 60% of the maximal intensity (W) differed favoring HD (p ≤ 0.05). Conclusion: Therefore, PC may contribute to increase aerobic capacity through the improvement of fat oxidation, maximum heart rate and perceptual responses during exercise.

Brown adipose tissue and regulation of human body weight

BACKGROUND

Approximately 30% of the global population is affected by obesity. Traditional non-surgical measures for weight loss have limited efficacy and tolerability. Therefore, there is a need for novel, effective therapies. Brown adipose tissue (BAT) has been implicated in physiological energy expenditure, indicating that it could be targeted to achieve weight loss in humans. The use of ¹⁸ F-fluorodeoxyglucose (¹⁸ F-FDG) positron emission tomography-computed tomography-(PET-CT) imaging has enabled the discovery of functionally active BAT in the supraclavicular, subclavian, and thoracic spine regions of human adults. This review aims to discuss the reasons behind the renewed interest in BAT, assess whether it is metabolically important in humans, and evaluate its feasibility as a therapeutic target for treating obesity.

SOURCES OF MATERIAL

PubMed Central, Europe PMC, Medline.

FINDINGS

In vivo studies have shown that BAT activity is regulated by thyroid hormones and the sympathetic nervous system. Furthermore, BAT uniquely contains uncoupling protein 1 (UCP1) that is largely responsible for non-shivering thermogenesis. Cold exposure can increase BAT recruitment through the browning of white adipose tissue (WAT); however, this technique has practical limitations that may preclude its use. Currently available medicines for humans, such as the β3-adrenergic receptor agonist mirabegron or the farnesoid X receptor agonist obeticholic acid, have generated excitement, although adverse effects are a concern. Capsinoids represent a tolerable alternative, which require further investigation.

CONCLUSIONS

The use of currently available BAT-activating agents alone is unlikely to achieve significant weight loss in humans. A combination of BAT activation with physical exercise and modern, successful dietary strategies represents a more realistic option.

Dihydrocapsiate does not increase energy expenditure nor fat oxidation during aerobic exercise in men with overweight/obesity: a randomized, triple-blinded, placebo-controlled, crossover trial

Background

Prior evidence suggests that capsinoids ingestion may increase resting energy expenditure (EE) and fat oxidation (FATox), yet whether they can modulate those parameters during exercise conditions remains poorly understood. We hypothesized that dihydrocapsiate (DHC) ingestion would increase EE and specifically FATox during an acute bout of aerobic exercise at FATmax intensity (the intensity that elicits maximal fat oxidation during exercise [MFO]) in men with overweight/obesity. Since FATmax and MFO during aerobic exercise appear to be indicators of metabolic flexibility, whether DHC has an impact on FATox in this type of population is of clinical interest.

Methods

A total of 24 sedentary men (age = 40.2 ± 9.2 years-old; body mass index = 31.6 ± 4.5 kg/m2 [n = 11 overweight, n = 13 obese]) participated in this randomized, triple-blinded, placebo-controlled, crossover trial (registered under ClinicalTrials.gov Identifier no. NCT05156697). On the first day, participants underwent a submaximal exercise test on a cycle ergometer to determine their MFO and FATmax intensity during exercise. After 72 hours had elapsed, the participants returned on 2 further days (≥ 72 hours apart) and performed a 60 min steady-state exercise bout (i.e. cycling at their FATmax, constant intensity) after ingesting either 12 mg of DHC or placebo; these conditions were randomized. Respiratory gas exchange was monitored by indirect calorimetry. Serum marker concentrations (i.e. glucose, triglycerides, non-esterified fatty acids (NEFAs), skin temperature, thermal perception, heart rate, and perceived fatigue) were assessed.

Results

There were no significant differences (P > 0.05) between DHC and placebo conditions in the EE and FATox during exercise. Similarly, no significant changes were observed in glucose, triglycerides, or NEFAs serum levels, neither in the skin temperature nor thermal perception across conditions. Heart rate and perceived fatigue did not differ between conditions.

Conclusions

DHC supplementation does not affect energy metabolism during exercise in men with overweight/obesity.

Bulk Process for Enrichment of Capsinoids from Capsicum Fruit

Various methods to synthesize capsinoids (the nonpungent analogs of capsaicinoids) from precursor molecules have been reported. Capsinoids are also naturally present, at typically low concentrations, in the fruit of many Capsicum species and genotypes. However, they are also present in the fruit of select genotypes at high concentrations. The fruit of high-capsiate genotypes represents a commercial source of these compounds. To date, no method has been published that efficiently extracts and purifies capsinoids from Capsicum fruit in a rapid and simple bulk process. This study evaluated the efficacy of various organic solvents for the extraction of capsinoids from dried Capsicum annuum fruit. Among the organic solvents evaluated, pentane appeared to provide a good combination of both recovery and purity. A subsequent liquid/liquid extraction step, utilizing pentane and acetonitrile, resulted in 26.3 % (wt/wt) capsiate and 19.4 % (wt/wt) dihydrocapsiate for a combined capsinoids yield of 45.7 % (wt/wt). A third step, involving a rapid hp20ss chromatography column using a water/acetonitrile gradient, resulted in a combined capsinoids yield of 96.6 % (wt/wt).

Mucin secretory action of capsaicin prevents high fat diet-induced gut barrier dysfunction in C57BL/6 mice colon

The gut barrier - including tight junction proteins (TJPs) and mucus layers, is the first line of defense against physical, chemical or pathogenic incursions. This barrier is compromised in various health disorders. Capsaicin, a dietary agonist of Transient receptor potential vanilloid 1 (TRPV1) channel, is reported to alleviate the complications of obesity. While it is well known to improve energy expenditure and metabolism, and prevent dysbiosis, the more local effects on the host gut - particularly the gut barrier and mucus system remain elusive. To investigate the effect of capsaicin on the gut barrier and mucus production and to understand the involvement of mucus, bacteria, and TRPV1 in these phenomena, we employed a diet-induced obesity model in C57BL/6 mice, and capsaicin (2 mg/kg/day p.o.) or mucin (1 g/kg/day p.o.) as interventions, for 12 weeks. Parameters like weight gain, glucose homeostasis, TJPs expression, mucus staining, intestinal permeability etc were studied. 16 S rDNA sequencing and in vitro Ca²⁺ measurement experiments were performed to explore the role of microbiota in the beneficial effects. Mucin feeding reflected several anti-obesity effects produced by capsaicin, suggesting that mucus modulation might play a crucial role in capsaicin-induced anti-obesity effects. 16 S rDNA sequencing and in vitro Ca²⁺ measurement experiments pointed to TRPV1 modulation by bacteria besides capsaicin. Capsaicin, bacteria and the host mucus system seem to act in a cyclic cascade involving TRPV1, which can be activated by capsaicin and various bacteria. These findings provide new insight into the role of TRPV1 in maintaining a healthy gut environment.

Sweet pepper and its principle constituent capsiate: functional properties and health benefits

Capsiate is a non-pungent analogue of capsaicin. It belongs to the family of capsinoids which are esters of vanillyl alcohol with fatty acids while capsaicin belongs to the family of capsaicinoids that are amides of vanillylamine with a variety of branched-chain fatty acids. While capsaicin is extensively reported for plethora of pharmacological actions, capsiate remains much less explored. Extracted from various species of Capsicum plant, the molecule has also been chemically synthesized via a number of synthetic and enzymatic routes. Based on its action on transient receptor potential vanilloid subfamily member 1 receptors, recent research has focused on its potential roles in treatment of obesity, metabolic disorders, cancer, cardiovascular disorders and gastro-intestinal disorders. Its toxicity profile has been reported to be much safe. The molecule, however, faces the challenge of low aqueous solubility and stability. It has been commercialized for its use as a weight loss supplement. However, the therapeutic potential of the compound which is much beyond boosting metabolism remains unexplored hitherto. This comprehensive review summarizes the studies demonstrating the therapeutic potential of capsiate in various pathological conditions. Discussed also are potential future directions for formulation strategies to develop efficient, safe and cost-effective dosage forms of capsiate to explore its role in various disease conditions. The databases investigated include Cochrane library, Medline, Embase, Pubmed and in-house databases. The search terms were "capsiate," "capsinoids," "thermogenesis," and their combinations. The articles were screened for relevance by going through their abstract. All the articles pertaining to physicochemical, physiological, pharmacological and therapeutic effects of capsiate have been included in the manuscript.

Effects of Capsinoid Intake on Brown Adipose Tissue Vascular Density and Resting Energy Expenditure in Healthy, Middle-Aged Adults: A Randomized, Double-Blind, Placebo-Controlled Study

Capsinoids are some of the most promising ingredients to increase energy expenditure (EE) due to brown adipose tissue (BAT) activation. However, there is limited information regarding the effect of prolonged capsinoid ingestion (CI) on BAT activity and resting EE (REE) in healthy, middle-aged, normal to overweight subjects (Sub_healthy) with distinct BAT characteristics. We examined the changes in BAT density (BAT-d), using near-infrared time-resolved spectroscopy, and REE/kg induced by daily CI. Forty Sub_healthy [age, 43.8 (mean) years; BMI, 25.4 kg/m²] received either capsinoid (9 mg/day) or a placebo daily for 6 weeks in a double-blind design. Total hemoglobin concentration in the supraclavicular region ([total-Hb]_sup), an indicator of BAT-d, and REE/kg were measured. The changes in post-intervention [total-Hb]_sup were greater in the capsinoid group (CA-G) than in the placebo group (PL-G) [5.8 µM (+12.4%) versus 1.0 µM (+2.1%); p = 0.017]. There was a significant relationship between BAT-d and REE/kg; however, post-supplementation REE/kg was not significantly different between the two groups (p = 0.228). In the overweight subgroup, changes in REE/kg were greater in the CA-G than in the PL-G [0.6 cal/kg/min (+4.3%) versus -0.3 cal/kg/min (-2.1%); p = 0.021]. CI enhanced [total-Hb]_sup, a reflection of BAT-d, showing a good correlation with REE in Sub_healthy.

Feeding brown fat: dietary phytochemicals targeting non-shivering thermogenesis to control body weight

Excessive adipose accumulation, which is the main driver for the development of secondary metabolic complications, has reached epidemic proportions and combined pharmaceutical, educational and nutritional approaches are required to reverse the current rise in global obesity prevalence rates. Brown adipose tissue (BAT) is a unique organ able to dissipate energy and thus a promising target to enhance BMR to counteract a positive energy balance. In addition, active BAT might support body weight maintenance after weight loss to prevent/reduce relapse. Natural products deliver valuable bioactive compounds that have historically helped to alleviate disease symptoms. Interest in recent years has focused on identifying nutritional constituents that are able to induce BAT activity and thereby enhance energy expenditure. This review provides a summary of selected dietary phytochemicals, including isoflavones, catechins, stilbenes, the flavonoids quercetin, luteolin and resveratrol as well as the alkaloids berberine and capsaicin. Most of the discussed phytochemicals act through distinct molecular pathways e.g. sympathetic nerve activation, AMP-kinase signalling, SIRT1 activity or stimulation of oestrogen receptors. Thus, it might be possible to utilise this multitude of pathways to co-activate BAT using a fine-tuned combination of foods or combined nutritional supplements.

Improvement of Lipid and Glucose Metabolism by Capsiate in Palmitic Acid-Treated HepG2 Cells via Activation of the AMPK/SIRT1 Signaling Pathway

Capsiate, a nonpungent ingredient of CH-19 Sweet, exhibits anti-obesity effects on animals and humans. This study investigated the effects and molecular mechanism of capsiate on lipid and glucose metabolism in PA-treated HepG2 cells. Results showed that compared with the PA-alone group, 100 μM capsiate inhibited lipid accumulation, decreased TG (0.0562 ± 0.0142 vs 0.0381 ± 0.0055 mmol/g of protein; P = 0.024) and TC (0.1087 ± 0.0037 vs 0.0359 ± 0.0059 mmol/g of protein; P = 0.000) levels, and increased the HDL-C level (0.0189 ± 0.0067 vs 0.1050 ± 0.0106 mmol/g of protein; P = 0.000) and glycogen content (0.0065 ± 0.0007 vs 0.0146 ± 0.0008 mg/10⁶ cells; P = 0.000) of PA-treated HepG2 cells; 100 μM capsiate also upregulated the level of CD36 ( P = 0.000), phosphorylation of ACC ( P = 0.034), and expression of CPT1 ( P = 0.013) in PA-treated HepG2 cells, leading to an enhancement of lipid metabolism. Meanwhile, 100 μM capsiate upregulated the levels of GLUT1, GLUT4, GK, and phosphorylation of GS ( P = 0.001, 0.029, 0.000, and 0.045, respectively) and downregulated the PEPCK level ( P = 0.001) to improve glucose metabolism in PA-treated HepG2 cells. Furthermore, the levels of phosphorylation of AMPK and expression of SIRT1 in HepG2 cells were increased by a 100 μM capsiate treatment ( P = 0.001 and 0.000, respectively), while the FGF21 level was decreased ( P = 0.003). Most of these effects were reversed by pretreatment with compound C, a selective AMPK inhibitor. Thus, capsiate might improve lipid and glucose metabolism in HepG2 cells by activating the AMPK/SIRT1 signaling pathway.

Capsaicin in Metabolic Syndrome

Capsaicin, the major active constituent of chilli, is an agonist on transient receptor potential vanilloid channel 1 (TRPV1). TRPV1 is present on many metabolically active tissues, making it a potentially relevant target for metabolic interventions. Insulin resistance and obesity, being the major components of metabolic syndrome, increase the risk for the development of cardiovascular disease, type 2 diabetes, and non-alcoholic fatty liver disease. In vitro and pre-clinical studies have established the effectiveness of low-dose dietary capsaicin in attenuating metabolic disorders. These responses of capsaicin are mediated through activation of TRPV1, which can then modulate processes such as browning of adipocytes, and activation of metabolic modulators including AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor α (PPARα), uncoupling protein 1 (UCP1), and glucagon-like peptide 1 (GLP-1). Modulation of these pathways by capsaicin can increase fat oxidation, improve insulin sensitivity, decrease body fat, and improve heart and liver function. Identifying suitable ways of administering capsaicin at an effective dose would warrant its clinical use through the activation of TRPV1. This review highlights the mechanistic options to improve metabolic syndrome with capsaicin.

Synthesis of (±)-3,4-dimethoxybenzyl-4-methyloctanoate as a novel internal standard for capsinoid determination by HPLC-ESI-MS/MS(QTOF)

Capsinoids exhibit health-promoting properties and are therefore compounds of interest for medical and food sciences. They are minor compounds present in relatively high concentrations in only a few number of pepper cultivars. It is desirable to quantify capsinoids to provide selected cultivars with high capsinoid contents, which can then be employed as health food product. Quantifying low concentrations of capsinoids from pepper fruit requires a precise and selective analytical technique such as HPLC coupled to electrospray ionization - mass spectrometry, with development of an internal standard essential. In this work, the synthesis method of a novel compound analogue of capsinoids, the (±)-3,4-dimethoxybenzyl-4-methyloctanoate, which could be a suitable internal standard for capsinoid determination by electrospray ionization - mass spectrometry is described.

(±)-3,4-dimethoxybenzyl-4-methyloctanoate was stable under the analysis conditions and exerted chemical and physical properties similar to those of capsinoids. This internal standard will provide an accurate capsinoid determination by electrospray ionization - mass spectrometry, thus facilitating the pepper breeding programs, screening pepper cultivars and a better understanding of capsinoid biosynthetic pathway.

Dihydrocapsiate supplementation prevented high-fat diet-induced adiposity, hepatic steatosis, glucose intolerance, and gut morphological alterations in mice

Despite the lipolytic and thermogenic properties of capsaicin, its putative use as a weight-lowering dietary supplement has been limited because of the burning sensation caused by capsaicin when it comes in contact with mucous membranes. A potential alternative to capsaicin are the capsinoids, nonpungent capsaicin analogs that exhibit effects similar to capsaicin. Whereas the antiobesity properties of capsinoids have been reported, the effectiveness of FDA-approved synthetic dihydrocapsiate has not yet been investigated. In the present study, we hypothesized that dihydrocapsiate might ameliorate high-fat diet (HFD)-induced metabolic disorders in a manner similar to capsaicin and therefore can be its nonpungent alternative. To test this hypothesis, HFD-fed mice were orally administered dihydrocapsiate (2 and 10mg/kg body weight) for 12weeks. Dihydrocapsiate modestly reduced the HFD-induced weight gain and significantly prevented the associated hyperglyceridemia and hyperinsulinemia while improving glucose tolerance. Histological and gene expression analysis showed that dihydrocapsiate significantly prevented the lipid accumulation in white adipose tissue and brown adipose tissue via targeting genes involved in energy expenditure and mitochondrial biogenesis, respectively. Dihydrocapsiate corrected hepatic triglyceride concentrations and normalized expression of genes regulating hepatic lipid and glucose metabolism. Moreover, dihydrocapsiate administration significantly improved gut morphology and altered gut microbial composition, resulting in reduced host energy availability. Collectively, these results indicate that dihydrocapsiate administration improved glucose tolerance, prevented adiposity and hepatic steatosis, as well as improved HFD-induced gut alterations, positing dihydrocapsiate as a potential food ingredient for the dietary management of HFD-induced metabolic alterations.

Dihydrocapsiate improved age-associated impairments in mice by increasing energy expenditure

Metabolic dysfunction is associated with aging and results in age-associated chronic diseases, including type 2 diabetes mellitus, cardiovascular disease, and stroke. Hence, there has been a focus on increasing energy expenditure in aged populations to protect them from age-associated diseases. Dihydrocapsiate (DCT) is a compound that belongs to the capsinoid family. Capsinoids are capsaicin analogs that are found in nonpungent peppers and increase whole body energy expenditure. However, their effect on energy expenditure has been reported only in young populations, and to date the effectiveness of DCT in increasing energy expenditure in aged populations has not been investigated. In this study, we investigated whether DCT supplementation in aged mice improves age-associated impairments. We obtained 5-wk-old and 1-yr-old male C57BL/6J mice and randomly assigned the aged mice to two groups, resulting in a total of three groups: 1) young mice, 2) old mice, and 3) old mice supplemented with 0.3% DCT. After 12 wk of supplementation, blood and tissue samples were collected and analyzed. DCT significantly suppressed age-associated fat accumulation, adipocyte hypertrophy, and liver steatosis. In addition, the DCT treatment dramatically suppressed age-associated increases in hepatic inflammation, immune cell infiltration, and oxidative stress. DCT exerted these suppression effects by increasing energy expenditure linked to upregulation of both the oxidative phosphorylation gene program and fatty acid oxidation in skeletal muscle. These results indicate that DCT efficiently improves age-associated impairments, including liver steatosis and inflammation, in part by increasing energy expenditure via activation of the fat oxidation pathway in skeletal muscle.

Factors involved in white-to-brown adipose tissue conversion and in thermogenesis: a review

Obesity is the result of energy intake chronically exceeding energy expenditure. Classical treatments against obesity do not provide a satisfactory long-term outcome for the majority of patients. After the demonstration of functional brown adipose tissue in human adults, great effort is being devoted to develop therapies based on the adipose tissue itself, through the conversion of fat-accumulating white adipose tissue into energy-dissipating brown adipose tissue. Anti-obesity treatments that exploit endogenous, pharmacological and nutritional factors to drive such conversion are especially in demand. In the present review, we summarize the current knowledge about the various molecules that can be applied in promoting white-to-brown adipose tissue conversion and energy expenditure and the cellular mechanisms involved.

Practical large-scale production of dihydrocapsiate, a nonpungent capsaicinoid-like substance

Capsinoids represent a novel group of capsaicinoid-like substances found in a nonpungent cultivar, Capsicum annuum “CH-19 Sweet.” They have capsaicinoid-like physiological and biological properties while lacking the harmful stimuli of capsaicinoids. A large-scale synthesis of dihydrocapsiate (DCT) is established in this work. 8-Methynonanoic acid (MNA) was synthesized by copper-catalyzed cross-coupling of ethyl 6-bromohexanoate with isobutylmagnesium bromide and subsequent hydrolysis. Lipase-catalyzed chemoselective esterification of vanillyl alcohol and MNA was performed at 50 °C under reduced pressure to remove water without solvents or drying agents. A slightly larger stoichiometric amount of MNA was used and the purification in the final stage was simplified to leave a small amount of MNA in the product, because we found that the presence of a small amount of MNA is necessary to stabilize DCT. DCT was synthesized according to the production, and stabilization methods described here has been filed as a new dietary ingredient.

Assessment of human brown adipose tissue density during daily ingestion of thermogenic capsinoids using near-infrared time-resolved spectroscopy

18F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDGPET/CT) is widely used as a standard method for evaluating human brown adipose tissue (BAT), a recognized therapeutic target of obesity. However, a longitudinal BAT study using FDG-PET/CT is lacking owing to limitations of the method. Near-infrared time-resolved spectroscopy (NIR(TRS)) is a technique for evaluating human BAT density noninvasively. This study aimed to test whether NIRTRS could detect changes in BAT density during or after long-term intervention. First, using FDG-PET/CT, we confirmed a significant increase (+48.8%, P < 0.05) in BAT activity in the supraclavicular region after 6-week treatment with thermogenic capsaicin analogs, capsinoids. Next, 20 volunteers were administered either capsinoids or placebo daily for 8 weeks in a double-blind design, and BAT density was measured using NIR(TRS) every 2 weeks during the 8-week treatment period and an 8-week period after stopping treatment. Consistent with FDG-PET/CT results, NIR(TRS) successfully detected an increase in BAT density during the 8-week treatment (+46.4%, P < 0.05), and a decrease in the 8-week follow-up period (-12.5%, P = 0.07), only in the capsinoid-treated, but not the placebo, group. Thus, NIR(TRS) can be applied for quantitative assessment of BAT in longitudinal intervention studies in humans.

A Synergistic Antiobesity Effect by a Combination of Capsinoids and Cold Temperature Through Promoting Beige Adipocyte Biogenesis

Beige adipocytes emerge postnatally within the white adipose tissue in response to certain environmental cues, such as chronic cold exposure. Because of its highly recruitable nature and relevance to adult humans, beige adipocytes have gained much attention as an attractive cellular target for antiobesity therapy. However, molecular circuits that preferentially promote beige adipocyte biogenesis remain poorly understood. We report that a combination of mild cold exposure at 17°C and capsinoids, a nonpungent analog of capsaicin, synergistically and preferentially promotes beige adipocyte biogenesis and ameliorates diet-induced obesity. Gain- and loss-of-function studies show that the combination of capsinoids and cold exposure synergistically promotes beige adipocyte development through the β2-adrenoceptor signaling pathway. This synergistic effect on beige adipocyte biogenesis occurs through an increased half-life of PRDM16, a dominant transcriptional regulator of brown/beige adipocyte development. We document a previously unappreciated molecular circuit that controls beige adipocyte biogenesis and suggest a plausible approach to increase whole-body energy expenditure by combining dietary components and environmental cues.

Dietary Capsaicin Protects Cardiometabolic Organs from Dysfunction

Chili peppers have a long history of use for flavoring, coloring, and preserving food, as well as for medical purposes. The increased use of chili peppers in food is very popular worldwide. Capsaicin is the major pungent bioactivator in chili peppers. The beneficial effects of capsaicin on cardiovascular function and metabolic regulation have been validated in experimental and population studies. The receptor for capsaicin is called the transient receptor potential vanilloid subtype 1 (TRPV1). TRPV1 is ubiquitously distributed in the brain, sensory nerves, dorsal root ganglia, bladder, gut, and blood vessels. Activation of TRPV1 leads to increased intracellular calcium signaling and, subsequently, various physiological effects. TRPV1 is well known for its prominent roles in inflammation, oxidation stress, and pain sensation. Recently, TRPV1 was found to play critical roles in cardiovascular function and metabolic homeostasis. Experimental studies demonstrated that activation of TRPV1 by capsaicin could ameliorate obesity, diabetes, and hypertension. Additionally, TRPV1 activation preserved the function of cardiometabolic organs. Furthermore, population studies also confirmed the beneficial effects of capsaicin on human health. The habitual consumption of spicy foods was inversely associated with both total and certain causes of specific mortality after adjustment for other known or potential risk factors. The enjoyment of spicy flavors in food was associated with a lower prevalence of obesity, type 2 diabetes, and cardiovascular diseases. These results suggest that capsaicin and TRPV1 may be potential targets for the management of cardiometabolic vascular diseases and their related target organs dysfunction.

Capsaicin and Related Food Ingredients Reducing Body Fat Through the Activation of TRP and Brown Fat Thermogenesis

Brown adipose tissue (BAT) is a site of sympathetically activated adaptive nonshivering thermogenesis, thereby being involved in the regulation of energy balance and body fatness. Recent radionuclide imaging studies have revealed the existence of metabolically active BAT in adult humans. Human BAT is activated by acute cold exposure and contributes to cold-induced increase in whole-body energy expenditure. The metabolic activity of BAT is lower in older and obese individuals. The inverse relationship between the BAT activity and body fatness suggests that BAT, because of its energy dissipating activity, is protective against body fat accumulation. In fact, repeated cold exposure recruits BAT in association with increased energy expenditure and decreased body fatness. The stimulatory effects of cold are mediated through the activation of transient receptor potential (TRP) channels, most of which are also chemesthetic receptors for various naturally occurring substances including herbal plants and food ingredients. Capsaicin and its analog capsinoids, representative agonists of TRPV1, mimic the effects of cold to decrease body fatness through the activation and recruitment of BAT. The well-known antiobesity effect of green tea catechins is also attributable to the activation of the sympathetic nerve and BAT system. Thus, BAT is a promising target for combating obesity and related metabolic disorders in humans.

A combination of exercise and capsinoid supplementation additively suppresses diet-induced obesity by increasing energy expenditure in mice

Exercise effectively prevents the development of obesity and obesity-related diseases such as type 2 diabetes. Capsinoids (CSNs) are capsaicin analogs found in a nonpungent pepper that increase whole body energy expenditure. Although both exercise and CSNs have antiobesity functions, the effectiveness of exercise with CSN supplementation has not yet been investigated. Here, we examined whether the beneficial effects of exercise could be further enhanced by CSN supplementation in mice. Mice were randomly assigned to four groups: 1) high-fat diet (HFD, Control), 2) HFD containing 0.3% CSNs, 3) HFD with voluntary running wheel exercise (Exercise), and 4) HFD containing 0.3% CSNs with voluntary running wheel exercise (Exercise + CSN). After 8 wk of ingestion, blood and tissues were collected and analyzed. Although CSNs significantly suppressed body weight gain under the HFD, CSN supplementation with exercise additively decreased body weight gain and fat accumulation and increased whole body energy expenditure compared with exercise alone. Exercise together with CSN supplementation robustly improved metabolic profiles, including the plasma cholesterol level. Furthermore, this combination significantly prevented diet-induced liver steatosis and decreased the size of adipocyte cells in white adipose tissue. Exercise and CSNs significantly increased cAMP levels and PKA activity in brown adipose tissue (BAT), indicating an increase of lipolysis. Moreover, they significantly activated both the oxidative phosphorylation gene program and fatty acid oxidation in skeletal muscle. These results indicate that CSNs efficiently promote the antiobesity effect of exercise, in part by increasing energy expenditure via the activation of fat oxidation in skeletal muscle and lipolysis in BAT.

A single intake of capsiate improves mechanical performance and bioenergetics efficiency in contracting mouse skeletal muscle

Capsiate is known to increase whole body oxygen consumption possibly via the activation of uncoupling processes, but its effect at the skeletal muscle level remains poorly documented and conflicting. To clarify this issue, gastrocnemius muscle function and energetics were investigated in mice 2 h after a single intake of either vehicle (control) or purified capsiate (at 10 or 100 mg/kg body wt) through a multidisciplinary approach combining in vivo and in vitro measurements. Mechanical performance and energy pathway fluxes were assessed strictly noninvasively during a standardized electrostimulation-induced exercise, using an original device implementing 31-phosphorus magnetic resonance spectroscopy, and mitochondrial respiration was evaluated in isolated saponin-permeabilized fibers. Compared with control, both capsiate doses produced quantitatively similar effects at the energy metabolism level, including an about twofold decrease of the mitochondrial respiration sensitivity for ADP. Interestingly, they did not alter either oxidative phosphorylation or uncoupling protein 3 gene expression at rest. During 6 min of maximal repeated isometric contractions, both doses reduced the amount of ATP produced from glycolysis and oxidative phosphorylation but increased the relative contribution of oxidative phosphorylation to total energy turnover (+28 and +21% in the 10- and 100-mg groups, respectively). ATP cost of twitch force generation was further reduced in the 10- (-35%) and 100-mg (-45%) groups. Besides, the highest capsiate dose also increased the twitch force-generating capacity. These data present capsiate as a helpful candidate to enhance both muscle performance and oxidative phosphorylation during exercise, which could constitute a nutritional approach for improving health and preventing obesity and associated metabolic disorders.

Nicotine from edible Solanaceae and risk of Parkinson disease

OBJECTIVE

To test whether risk of Parkinson disease (PD) is associated with consumption of nicotine-containing edibles from the same botanical family as tobacco, Solanaceae, including peppers, tomatoes, and potatoes.

METHODS

In a population-based study with 490 newly diagnosed idiopathic PD cases diagnosed during 1992-2008 at the University of Washington Neurology Clinic or Group Health Cooperative in western Washington State and 644 unrelated, neurologically normal controls, we examined whether PD was associated with self-reported typical frequency of consumption of peppers, tomatoes, tomato juice, and potatoes during adulthood, while adjusting for consumption of other vegetables, age, sex, race/ethnicity, tobacco use, and caffeine.

RESULTS

PD was inversely associated with consumption of all edible Solanaceae combined (relative risk [RR] = 0.81, 95% confidence interval [CI] = 0.65-1.01 per time per day), but not consumption of all other vegetables combined (RR = 1.00, 95% CI = 0.92-1.10). The trend strengthened when we weighted edible Solanaceae by nicotine concentration (ptrend = 0.004). An inverse association was also evident for peppers specifically (ptrend = 0.005). The potentially protective effect of edible Solanaceae largely occurred in men and women who had never used tobacco or who had smoked cigarettes < 10 years.

INTERPRETATION

Dietary nicotine or other constituents of tobacco and peppers may reduce PD risk. However, confirmation and extension of these findings are needed to strengthen causal inferences that could suggest possible dietary or pharmaceutical interventions for PD prevention.

Natural products and body weight control

The purpose of the review was to summarise the effect of some commonly available natural products used for body weight management. We collected data from PubMed and scientific journals. There are numerous publications on this topic, however we have summarized the most commonly available and potent natural products from recent 53 publications. The natural products analyzed in this paper include catechins, capsaicin, conjugated linoleic acid, fucoxanthin, soy isoflavone, glabridin, astaxanthin and cyaniding-3-glucoside. These natural products are effective and safe for body weight management. Further studies need to be conducted to investigate the mechanism of action, metabolism, long term safety and side effects of these natural products, as well as interactions between these natural products with dietary components.

Activation of transient receptor potential A1 by a non-pungent capsaicin-like compound, capsiate

BACKGROUND AND PURPOSE

Capsiate is produced by 'CH-19 Sweet' (Capsicum annuun L.), a non-pungent cultivar of red pepper. Like capsaicin, capsiate is thought to enhance energy metabolism by activating the sympathetic nervous system and suppressing inflammation, but the underlying mechanisms for this are uncertain. We previously reported that capsiate could activate transient receptor potential vanilloid 1 (TRPV1), a capsaicin receptor. The purpose of the present study is to investigate whether capsinoids activate other TRP channels.

EXPERIMENTAL APPROACH

Using Ca(2+) imaging and whole-cell patch-clamp methods, we analysed the response of TRP channels to three kinds of capsinoids, capsiate, dihydrocapsiate and nordihydrocapsiate, in HEK293T cells expressing TRP channels or in primary cultures of mouse dorsal root ganglion neurons.

KEY RESULTS

We found that in both cell types TRP ankyrin 1 (TRPA1) had a slightly weaker response to capsinoids compared with TRPV1, with the capsiate EC(50) for TRPA1 activation being more than that for TRPV1 activation, and that the capsinoid-evoked action was blocked by a specific TRPA1 antagonist. TRPA1 was activated by capsinoids, but not by their degradation products. Amino acids known to participate in TRPA1 activation following cysteine covalent modification or zinc treatment were not involved in the activation of TRPA1 by capsinoid.

CONCLUSIONS AND IMPLICATIONS

Taken together, these results indicate that capsinoids activate TRPA1 by an as yet unknown mechanism, and TRPA1 could be involved in physiological phenomena associated with capsinoid treatment.

Molecular biology of capsaicinoid biosynthesis in chili pepper (Capsicum spp.)

Capsicum species produce fruits that synthesize and accumulate unique hot compounds known as capsaicinoids in placental tissues. The capsaicinoid biosynthetic pathway has been established, but the enzymes and genes participating in this process have not been extensively studied or characterized. Capsaicinoids are synthesized through the convergence of two biosynthetic pathways: the phenylpropanoid and the branched-chain fatty acid pathways, which provide the precursors phenylalanine, and valine or leucine, respectively. Capsaicinoid biosynthesis and accumulation is a genetically determined trait in chili pepper fruits as different cultivars or genotypes exhibit differences in pungency; furthermore, this characteristic is also developmentally and environmentally regulated. The establishment of cDNA libraries and comparative gene expression studies in pungent and non-pungent chili pepper fruits has identified candidate genes possibly involved in capsaicinoid biosynthesis. Genetic and molecular approaches have also contributed to the knowledge of this biosynthetic pathway; however, more studies are necessary for a better understanding of the regulatory process that accounts for different accumulation levels of capsaicinoids in chili pepper fruits.

Intraluminal administration of zingerol, a non-pungent analogue of zingerone, inhibits colonic motility in rats

Zingerone, a pungent component of ginger, may exert beneficial therapeutic effects on hypermotility-induced diarrhea because it has the ability to inhibit contractions of colonic smooth muscles. However, the pungency is undesirable for possible therapeutic use. The purpose of this study was to examine effects of zingerol, a non-pungent analogue of zingerone, in rats. Colonic motility in vivo was evaluated by measuring intraluminal pressure changes and expelled fluid volume from the colon in anesthetized rats. Mechanical contractile activities of isolated colonic segments were also recorded. Intracolonic administration of zingerol attenuated colonic motility in vivo without affecting blood pressure and heart rate in a manner similar to that of zingerone. Zingerol also inhibited spontaneous contractile movements in isolated colonic segments, suggesting that zingerol directly acts on the colon. Zingerol had no effect on jejunal motility, although zingerone showed an inhibitory effect to the jejunum. These findings suggest that zingerol can inhibit colonic motility without adverse effects on small intestinal motility and the cardiovascular system. The non-pungent property of zingerol will be useful as an oral or suppository medicine for treating diarrhea and other gastrointestinal disorders.

Novel loss-of-function putative aminotransferase alleles cause biosynthesis of capsinoids, nonpungent capsaicinoid analogues, in mildly pungent chili peppers (Capsicum chinense)

Capsinoids are a group of nonpungent capsaicinoid analogues produced in Capsicum fruits. They have similar bioactivities to capsaicinoids such as suppression of fat accumulation and antioxidant activity. They are more palatable ingredients in dietary supplements than capsaicinoids because of their low pungency. Previous studies on nonpungent Capsicum annuum cultivars showed that capsinoid biosynthesis is caused by loss-of-function putative aminotransferase (p-amt) alleles. This study showed that three mildly pungent cultivars of Capsicum chinense (Zavory Hot, Aji Dulce strain 2, and Belize Sweet) contain high levels of capsinoid. It was shown that these cultivars have novel p-amt alleles, which contain mutations that differ from those of C. annuum. Sequence analysis of p-amt in Belize Sweet revealed that a 5 bp insertion (TGGGC) results in a frameshift mutation. A transposable element (Tcc) was found in the p-amt of Zavory Hot and Aji Dulce strain 2. Tcc has features similar to those of the hAT transposon family. This was inserted in the fifth intron of Zavory Hot and in third intron of Aji Dulce strain 2. The p-amt alleles harboring Tcc cannot produce an active p-AMT. These mildly pungent cultivars will provide a new natural source of capsinoids.

Intragastric administration of capsiate, a transient receptor potential channel agonist, triggers thermogenic sympathetic responses

The sympathetic thermoregulatory system controls the magnitude of adaptive thermogenesis in correspondence with the environmental temperature or the state of energy intake and plays a key role in determining the resultant energy storage. However, the nature of the trigger initiating this reflex arc remains to be determined. Here, using capsiate, a digestion-vulnerable capsaicin analog, we examined the involvement of specific activation of transient receptor potential (TRP) channels within the gastrointestinal tract in the thermogenic sympathetic system by measuring the efferent activity of the postganglionic sympathetic nerve innervating brown adipose tissue (BAT) in anesthetized rats. Intragastric administration of capsiate resulted in a time- and dose-dependent increase in integrated BAT sympathetic nerve activity (SNA) over 180 min, which was characterized by an emergence of sporadic high-activity phases composed of low-frequency bursts. This increase in BAT SNA was abolished by blockade of TRP channels as well as of sympathetic ganglionic transmission and was inhibited by ablation of the gastrointestinal vagus nerve. The activation of SNA was delimited to BAT and did not occur in the heart or pancreas. These results point to a neural pathway enabling the selective activation of the central network regulating the BAT SNA in response to a specific stimulation of gastrointestinal TRP channels and offer important implications for understanding the dietary-dependent regulation of energy metabolism and control of obesity.

Effect of dihydrocapsiate on resting metabolic rate in humans

BACKGROUND

Dihydrocapsiate is a capsinoid found in chili peppers. Dihydrocapsiate is similar to capsaicin, which is known for its thermogenic properties.

OBJECTIVE

The objective was to determine the acute and chronic effect of dihydrocapsiate on resting metabolic rate (RMR).

DESIGN

Seventy-eight healthy subjects in a double-blind, parallel-arm trial were randomly assigned to 3 groups receiving 0 (placebo), 3, or 9 mg dihydrocapsiate/d for 28 d. After a 10-h overnight fast, RMR was measured by indirect calorimetry for 30 min before and 120 min after ingestion of dihydrocapsiate.

RESULTS

RMR was similar in the 3 groups before dosing on day 1 [1714 ± 41 kcal/d (0 mg), 1760 ± 41 kcal/d (3 mg), and 1694 ± 38 kcal/d (9 mg)] and after acute dosing (41 ± 17, 55 ± 17, and 3 ± 24 kcal/d for 3-mg, 9-mg, and placebo groups, respectively). When the chronic effect of dihydrocapsiate on RMR was calculated from the average 2-h RMR on day 28 minus the 30-min preingestion RMR at baseline, a borderline effect in subjects receiving 3 mg dihydrocapsiate/d compared with placebo was observed (61 ± 24 kcal/d compared with -1 ± 12 kcal/d, P = 0.054), whereas no significant increase in RMR in comparison with placebo was noted for the 9-mg/d dose (48 ± 23 kcal/d compared with -1 ± 12 kcal/d, P = 0.12). When data from both groups were combined, the thermic effect of dihydrocapsiate reached significance (53 ± 9 kcal/d compared with -1 ± 12 kcal/d in the placebo group, P = 0.04). Fat oxidation was unaffected by dihydrocapsiate.

CONCLUSION

After 1 mo of supplementation, dihydrocapsiate had a small thermogenic effect of ≈50 kcal/d, which is in the range of day-to-day RMR variability. This trial was registered at clinicaltrials.gov as NCT00999297.

Recent advances in the study on capsaicinoids and capsinoids

Chili peppers are the major source of nature capsaicinoids, which consist of capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin, etc. Capsaicinoids are found to exert multiple pharmacological and physiological effects including the activities of analgesia, anticancer, anti-inflammation, antioxidant and anti-obesity. Therefore, capsaicinoids may have the potential value in clinic for pain relief, cancer prevention and weight loss. In addition, capsaicinoids also display the benefits on cardiovascular and gastrointestinal system. It has been shown that capsaicinoids are potential agonists of capsaicin receptor or transient receptor potential vanilloid subfamily member 1 (TRPV1). They could exert the effects not only through the receptor-dependent pathway but also through the receptor-independent one. CH-19 Sweet peppers are the source of nature capsinoids, which share similar structure with capsaicinoids and consist of capsiate, dihydrocapsiate, and nordihydrocapsiate, etc, Comparing with capsaicinoids, capsinoids are less pungent and easily broken down in the normal aqueous conditions. So far, it has been found that capsinoids possess the biological properties of antitumor, antioxidant and anti-obesity. Since capsinoids are less toxic than capsaicinoids, therefore, capsinoids may have the advantages over capsaicinoids in clinical applications such as cancer prevention and weight loss.

Effects of dihydrocapsiate on adaptive and diet-induced thermogenesis with a high protein very low calorie diet: a randomized control trial

Background

Dihydrocapsiate (DCT) is a natural safe food ingredient which is structurally related to capsaicin from chili pepper and is found in the non-pungent pepper strain, CH-19 Sweet. It has been shown to elicit the thermogenic effects of capsaicin but without its gastrointestinal side effects.

Methods

The present study was designed to examine the effects of DCT on both adaptive thermogenesis as the result of caloric restriction with a high protein very low calorie diet (VLCD) and to determine whether DCT would increase post-prandial energy expenditure (PPEE) in response to a 400 kcal/60 g protein liquid test meal. Thirty-three subjects completed an outpatient very low calorie diet (800 kcal/day providing 120 g/day protein) over 4 weeks and were randomly assigned to receive either DCT capsules three times per day (3 mg or 9 mg) or placebo. At baseline and 4 weeks, fasting basal metabolic rate and PPEE were measured in a metabolic hood and fat free mass (FFM) determined using displacement plethysmography (BOD POD).

Results

PPEE normalized to FFM was increased significantly in subjects receiving 9 mg/day DCT by comparison to placebo (p < 0.05), but decreases in resting metabolic rate were not affected. Respiratory quotient (RQ) increased by 0.04 in the placebo group (p < 0.05) at end of the 4 weeks, but did not change in groups receiving DCT.

Conclusions

These data provide evidence for postprandial increases in thermogenesis and fat oxidation secondary to administration of dihydrocapsiate.

Trial registration

clinicaltrial.govNCT01142687